Archive for September, 2024

Stop native extinction. Sure. But at what cost?

September 29, 2024

n30_w1150
n30_w1150 by BioDivLibrary is licensed under CC-PDM 1.0

A recent (23 September 2024) ABC 7:30 Report story, Back from Extinction, gave an interesting account of the Wild Deserts program that is aiming to reverse the trend toward native animal extinction in Australia. Fair enough. We don’t have a great record.

Bilbies, bandicoots, bettongs and quolls, once thought extinct in New South Wales for over a hundred years, are reclaiming parts of an outback NSW desert. (source: ABC 7:30 Report)

This seems to be a positive thing for the species and the ecosystem in which they once thrived.

About 6 minutes into the 7 minute clip, the discussion turns to controlling the causes of extinction, including feral animals, in particular cats. The method of control discussed in the program is a device that attracts a cat into a confined area such that a dose of 1080 poison is applied to its fur, which it then licks, ingests, so is poisoned and dies.

Sometimes, 1080 finds its way near locations in which pets live.

People described the death of their “loved one” from 1080 baiting as one of the most horrific experiences of their lives. Symptoms of 1080 poisoning included … vomiting, defecating, urinating, frenzied running … “screaming”, convulsions, confusion, fear, coma and finally, death. The Conversation

So, the suffering of a non-native animal doesn’t matter? Just collateral damage?

Of course the native species has to fight for survival in the ecosystem into which they’re introduced, but at least they have a fighting chance to live as opposed to being murdered for being the wrong species, in the wrong place (Australia), at the wrong time.

But, are they being reintroduced to “rebalance” or “re-engineer” the ecosystem or from which they were removed by us, or for their own “right” to live? Or both?

There is an idea, often unspoken, that native species have more value than non-native. Cats, dogs, livestock etc are not native to Australia. Neither are humans. Livestock are not native, but they are favoured by farmers over dingoes which have been here for thousands of years.

Being cute and cuddly shouldn’t be an important factor either but you would be forgiven for thinking so sometimes.

To be honest, I’m left with the feeling that both native and non-native feral species are often seen as a means to an end. That’s obviously true in the case of livestock.

As it turns out, I do not think that cats (for example) should be allowed to roam unsupervised in backyards or elsewhere, where that would result in harm to native animals whose species is in threat of extinction. Limiting freedom in this case seems to be a necessity, but that doesn’t mean it’s fair, and it doesn’t mean the pet should suffer.

It would seem that animals can go from being considered as a pet to a pest, depending upon location and negative impact in their environment, e.g. cat-as-pet vs cat-in-backyard-eating-birds or cat-as-feral. I’ve written elsewhere about another mammal that’s mostly considered a pest but that like most of us, is just trying to get on with its life.

Of course, all animals can be viewed as pests from the right point of view, all carry disease, all can do damage to ecosystems. Not to downplay the importance of the work being done by researchers in the Wild Deserts program, but it’s just interesting, and at times disturbing, to see the various ways in which we think we “know best”.

Finding Pluto with a Seestar

September 20, 2024

I’ve had a Seestar S50 since mid-August 2024. The S50 is a small refracting (f/5 apochromatic triplet) telescope with a focal length of 250mm, an aperture of 50mm, and a ZWO-based imaging system that can be controlled with an iOS or Android app.

Images can be taken, enhanced and accessed via the app but the FITS (Flexible Image Transport System, commonly used in astronomy) files can also be downloaded via USB cable for further processing on a computer. This includes photometry, to determine the brightness of targets such as variable stars or asteroids.

So far I’ve taken images of the Triffid nebula, planetary nebulae such as the Dumbbell and Helix nebulae, globular star clusters, the yet-to-erupt recurrent nova T Corona Borealis, a nova in Scorpius (V1725 Sco), a short period (79 minutes) pulsating variable (SX Phe), Luna during the daytime (just because), the Sun, and Pluto from my suburban backyard in South Australia.

I wanted to take two images a few days apart to show Pluto’s movement against the background stars. These images were taken on September 3 and 7:

Note that the images are “decorated” by information and cross hairs because this is a view of the field from the software Tycho Tracker that I use (primarily for variable star photometry).

Here is an animated GIF created from these two images to make the change in location of Pluto on the two dates more obvious. Focus your attention just to the upper right and lower left not far from the centre of the image.

Here are some undecorated images with arrows pointing at Pluto, on Sep 3 and Sep 7 (around 20 minutes of total exposure each, via multiple stacked 10 second exposures):

Pluto takes 248 years to orbit around the Sun at an average distance of almost 6 billion km.

How far did Pluto travel along its orbit between September 3 and 7?

At an average speed of 17,096 km/hour, over the 3.96 days between the images I took, Pluto travelled approximately 1,625,000 km. We could arrive at a better result with some trigonometry.

I also measured Pluto’s magnitude on September 7 at 14.64 +/- 0.05, very close to the catalogue value:

The image comparator below provides another way to reveal the location of Pluto on September 3 (upper right of red cross hairs) and September 7 (lower left of cross hairs), by moving the vertical line left or right.

Pluto on September 3 (upper right of cross hairs) and 7 (lower left of cross hairs)

Below are SkySafari Pro screenshots for comparison in case you want to check Pluto’s position for yourself on the dates and times in question.

Finally, compare the images from the S50 to those Clyde Tombaugh had to work with in 1930 when he discovered Pluto using a mechanical blink comparator!

Being able to see the movement of Pluto is something I’ve wanted to do for myself since Martin George showed me Pluto through the eyepiece of a 14 inch aperture reflecting telescope in Tasmania about 30 years ago.

Another talk about T CrB

September 14, 2024

I gave another talk about T CrB earlier this month and hoped I would be speaking post eruption by then.

We’re still waiting, and we’re about to lose it in the early evening sky.

I’ve been checking the area with binoculars most clear nights and doing some photometry with my Seestar S50.

Even if we miss the main event, we have another shot at seeing the nova rise about 100 days post-eruption.

V1725 Sco: π in the sky?

September 14, 2024

V1725 Sco

In September 2024, a nova was independently discovered in Scorpius by Koichi Itagaki (Japan) and Andrew Pearce (Western Australia). Its designation is V1725 Sco.

I like to think of the lovely asterism (arbitrary star grouping) in which the nova appears (arrowed above) as:

\; \pi \; in \; the \; sky

The visual band light curve below shows the nova’s (partial) rise to around magnitude 9.5 in early September to around magnitude 13 almost a month later.

I made (and submitted to AAVSO) 6 observations of the nova with my Seestar.

The differential photometry aperture rings (red bullseye) are centred on the nova and the green highlighted stars are reference stars. Note the deliberate defocus, so that the light of the stars is spread across multiple sensor pixels, as is common for “one-shot colour” sensors such as the S50, DSLRs and others. My tests so far suggest this may be less necessary than for the DSLR photometry I’ve done in the past, possibly because of the differences between sensor sizes and the number of arc seconds per pixel.

One of the things I love about doing variable star photometry is the endless variation in the star fields being imaged, and the endlessly varying asterisms I see and can imagine about.